Process of manufacturing balls and small articles of closed-cell cellular rubber



Dec, 26, 1933. M. P. H. L. RAEPSAET 11341 953 PROCESS OF MANUFACTURING BALLS AND SMALL ARTICLES OF CLOSED CELL CELLULAR RUBBER Filed Aug. 24, 1951 Patented Dec. 26, 1933 r nocnss OFIMANUFACTURINGYBALLS AND", "iSMALL ARTICLES. OF iCLOSED-CELL' CEL- *LULAR' RUBBER- Loire' (Haute Loire), France, assig'norto So- 1 ciete"Belge-' du- Gaoutchouc Mousse; Be'rchemlls, --Belgium, a corpora- ..ApplicationI"August;..24, 1931 Serial No.f 559,102, Y m an GelfmanyJuly 20,1931

, Claims; (01.18- -53) ltis known that-the essential operation in -the manufacture-of cellular rubber with closed cells, thatis to-say, consisting of a mass of rubberzcon- I .taining a' veryilarge, number of minute separate internal C8l1S,;,-; fi11d' Wlth gas, is' the r vulcanization of the mass of rubber containedin a'mquld, which is not gastight and is placed in an autoclave charged with a gaseous atmosphere under very high pressure. When the mass of rubber is somewhat thick, the gas does not penetrate as far as the core, and the vulcanization is not uniform, nor is the mass homogeneous.

The chief object of the invention now to be described is to facilitate'said penetration by the gas, and is characterized in that the roughmoulded article of raw rubber is provided with a certain number of channels, preferably radial, and

fitted, if necessary, with devices intended to prevent them from closing up during the aforesaid vulcanization.

On issuing from the vulcanizing mould, the balls expand considerably and exhibit protuberances due to the irregular distribution-of the gases in the peripheral layer, where the mass of rub ber is not perfectly homogeneous, some portions of said layer yielding more readily than the others These protuberances are more frequent-and extensive when the mass has been provided with the aforesaid channels, and cause them to assume the form of craters at the surface. 1 7

Moreover, a rough skin is formed on the surface of the ball, owing to rupture of the superficial cells. According to asecond feature ofthe invention, these imperfections are removed byf grindingthe surface of the ball before placing it in the expansion mould for the second baking.

Two typical methods of piercing the balls are hereinafter described, and are illustrated in the accompanying drawing.

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Figure 1 represents a plodder with capillary needles and Figure 2 a ball with needle in the position of piercing. diametrical section of the pierced rough and finished ball respectively. w v

According to Figure 1, the discharge opening 1 of the plodder is provided with a certain num- .ber of capillary needles 2, with enlarged points 3.

sage of the needles 2 has left channels 5, which remain open to a sufficient extent. The roll is cut up into portions 7 of the desired weight to forma ball, and the portion 7 is placed in a ballshaping mould, consisting of two hemispherical Figures 3 and '4 shew a- 7 The mass of hot, pasty rubber 4, impelledby the worm conveyor (not shewn) of the plodder,

forms, at the outlet, a roll 5,'in which the pascavities, in orderlt o shape it into azspherical blank.

The channel 6, whi ch still exist in the blank enablethehigh pressure; gases to penetrate into the core ofthe mass during the vulcanizing in the trates throughout the entire mass during vulcani- 'zation A diametrical section of the ball, onleaving the autoclave and after expanding (Fig; 4) shews that the entire mass has acquired a more uniform cellular texture than if the pierced channels were absent. The cells are slightly larger in the peripheral and central regions 13 and 14, and

traces of thechannels 11, 11' etc., are stilldiscernible. The existence of the central cavity makes the ball bounce better and reduces-the weight per given volume. f

In'the event of the channels formed by the needle or needles not remaining suihciently open to allow the high-pressure gases in the autoclave to penetrate freely, talc is injected, or a woolen In the autothreadpreferably untwisted, and dusted with talcis left in the channels' After the ball has freely expanded, on being; taken out of the mould which enclosed it in the autoclave, this ballhas an irregular and rugged surface, covered with a skin formed by contact with the mould and by the other layer of rubber, in which the cells have burst, the position of the pierced channels being indicated by craters. If

suchfla ball be heated in the expansion mould, creases might form on its surface. According to the invention, the ball is ground, to remove the skin and protuberances and approximate y re-' store its spherical shape. It is then'heated in an expansion. mould, where it acquires a highly uniform shape and surface.

What I claim is:'-

1. The process of manufacturing cellular rubber balls and other articles having closed cells containing gas under pressure consisting in drilling passages through the body of thecrude blanks "its "foo

by means of needles, placing the blanks in molds, introducing the molds in an autoclave filled with cii gas under high pressure, heating the blanks contained in the molds and thus partially vulcanizing them, taking the blanks out of the molds, grinding them until their surface is made smooth, placing the'blanks in a second series of molds and again heating them until vulcanization is complete.

2. The process of manufacturing cellular rubber balls and other articles having-closed cells containing gas under pressure consisting in discharging the crude rubber in form of cylinders from a press whose outlet is provided with longitudinal needles, shaping the crude rubber into blanks of the desired form, drilling passages through the body of the blanks by means of needles, placing the blanks in molds, introducing the molds in an autoclave filled with gas under high pressure, heating the blanks contained in the moldsand thus partially vulcanizing them, taking the blanks out of the moulds, grinding them until their surface is made smooth, placing the blanks in a second series of moulds and again heating them until vulcanization is complete.

3. The process of manufacturing cellular rubber balls with closed cells containing gas under pressure consisting in drilling passages through the body of the crude blanks up to, on slightly beyond the centre by means of needles, placing the blanks in moulds, introducing the moulds in an autoclave filled with gas under high pressure,

heating the blanks contained in the moulds and 30 .thus partially vulcanizing them, taking the blanks out of the moulds, grinding them until their surface is made smooth, placing the blanks in a second series of moulds and again heating them until vulcanization is complete.

4. The process of manufacturing cellular rubber ballsjand other articles having closed cells containing gas under pressure consisting in drilling passages through the body of the crude blanks by means of needles and introducing into these passages a strand of wool which is not twisted and which is impregnated with talc, placing the blanks in moulds, introducingthe moulds in an autoclave filled with gas under high pressure, heating the blanks contained in the moulds and thus partially vulcanizing them, taking the blanks out of the moulds, grinding them until their surface is made smooth, placing the blanks in a second series of moulds and again heating them until vulcanization is complete.

MAURICE PAUL HENRI LEON RAEPSAET. 

